the concept 300 does have evet recall, (sens and tell) so you can interogate it as to what casued the alarm, just remembering back, my concept 600 had a2 new bonnet switches but when the autostart was armed and then you shut the door it would disarm and not start - the sens and tell indicated that it was the bonnet switch , which had already been replaced - turned out to be where they had run the wire through the bulkhhead as sm says, (they rush) they hadn't fitted a grommet and it had fridged throughthe insulation of the cable and it was only when slamming a door it caused it move enough to earth out. another one to check anyway.